Sims joined the German outfit last season alongside Antonio Felix da Costa, in what was his maiden season in the all-electric category.
At the final race of the year in New York, Sims scored a second-place finish to claim his first podium finish in Formula E, ending the season 13th in the drivers' championship.
"I learned so much in my rookie year. There were fantastic highs and some lows to overcome and I’m determined to utilise this knowledge and start where I left off, continuing to build from there,” said Sims.
“The competition is set to be tough this season with the other drivers but I’ve got to grips with the unique challenges of Formula E and I’m ready to turn that experience into good results.”
For the sixth season of Formula E, da Costa will be joined by Max Gunther, who made his debut in the series last year racing for GEOX Dragon.
Gunther was confirmed at BMW in September, while Felx da Costa has joined reigning champions DS Techeetah alongside Jean-Eric Vergne.
BMW Group Motorsport Director Jens Marquardt added: “We have an exciting driver duo for our second Formula E season.
“Alexander Sims learned at a rapid pace in his first season, and showed that he can be up there at the front.
"He was unlucky in some of the races, but he finally celebrated his first podium at the finale in New York. I’m confident that he will be able to build on this in 2019/20.
Bahrain International Circuit - Winter testing